are immunosuppressive in vitro. High concentrations of sigma receptors are present on lymphoid and endocrine cells, suggesting that endogenous sigma ligands may be important in immune regulation and CNS-endocrine-immune integration. It has recently been discovered that sigma receptors are heterogeneous, and preliminary data suggest that multiple forms of sigma receptors may be functionally active in the immune system. The purpose of the proposed study is to determine whether multiple forms of sigma receptors are present on immune cells, to link specific subtypes of sigma receptors to functional activities, and to examine potential signal transduction mechanisms for these receptors in lymphocytes. To link sigma receptor subtypes to function we will: (1) conduct saturation radioligand binding experiments to determine whether multiple sigma binding sites are present in rat and mouse spleen, (2) conduct further saturation binding studies in cultured cell lines to determine whether multiple receptors exist on individual cells, or different cell types have different receptors, (3) pharmacologically characterize high and low affinity receptors using drug competition binding assays, (4) conduct still further saturation binding studies on commercially available T cell, B cell and macrophage/monocyte lines to determine which cell types have sigma receptors, and (5) determine which receptor type correlates with suppression of function (proliferation and lymphokine secretion) in the antigen-specific T-MBP-l rat helper T cell line. In light of sigma receptor heterogeneity, linkage of sigma receptor subtype to function is a necessary stage that must be accomplished to assure that later attempts to purify and clone the receptors deal with the appropriate entities. To study signal transducing mechanisms, we will use sigma agonists to modulate the triggering of antigen-specific T-MBP-l cells by their antigen receptors. We will measure intracellular free calcium by means of calcium-sensitive dye, and the actions of potassium channels will be observed using the patch-clamp technique. We will also examine the coupling of sigma receptor subtypes to guanine nucleotide regulatory proteins. The power of this model, using antigen-specific T cell lines, is that we can study a response to an antigenic stimulus in a highly defined cell population. This investigation is relevant to human health because potent sigma agonists (the "street" drugs PCP and cocaine, and the prescribed drugs haloperidol and chlorpromazine) are encountered by many humans. In addition, the T-MBP-l cell line causes an animal model of multiple sclerosis. Therefore, insights into the regulation of these cells would be directly applicable to a human disease process.